The present disclosure generally relates to the control of a supply of fuel in an internal combustion engine. More specifically, the present disclosure relates to a control system that interrupts the flow of fuel to an internal combustion engine when the engine has been turned off.
Small internal combustion engines are used to power lawn and garden equipment, walk behind lawn mowers, snow blowers, tillers, garden tractors, pressure washers, electrical generators and the like. Such engines include carburetors that receive fuel from a fuel tank. The fuel from the storage tank is mixed with air in a carburetor and the fuel/air mixture is supplied into an engine cylinder where the fuel/air mixture is ignited by a spark plug. Following ignition, during the exhaust stroke of the engine, the combustion gases are forced from the cylinder through a muffler.
In many applications of small internal combustion engines, the engine includes a kill switch that, when closed, shorts the electrical ignition system to ground to prevent further operation of the spark plugs. Although such a kill switch effectively kills the operation of the engine quickly, the engine does not immediately stop revolving but continues to revolve for several rotations due to the inertial forces of the moving components within the engine. During this continuing rotation, the movement of the piston within the cylinder continues to draw the fuel/air mixture from the carburetor into the cylinder. Since the spark plug ignition is interrupted, the unburned fuel mixture is forced from the cylinder into the heated muffler. When the muffler is sufficiently heated after a period of continuous operation, hot spots in the muffler can cause the ignition of the unburned fuel mixture. The ignition of the fuel mixture within the muffler creates a phenomenon called a backfire that not only generates a loud noise, but can damage the muffler.
One attempt to prevent the discharge of unburned fuel into a heated muffler utilizes an arrangement that prevents the flow of fuel into the carburetor almost immediately after operation of the kill switch. These fuel flow interrupt devices typically require a stored electrical charge from either a storage battery or storage capacitor to supply the power required to move a valve element to prevent the flow of fuel. In such systems, a storage capacitor is charged during operation of the internal combustion engine and, once the kill switch is activated, the stored charge from the storage capacitor is used to charge an electromagnetic coil that moves a valve element to restrict the flow of fuel into the carburetor.
In yet another system, a battery is included in the fuel supply system to move a fuel interrupt solenoid. However, in such a system, the battery requires an alternator to charge the battery during usage of an internal combustion engine. In each of the systems described above, additional circuitry is required to be included with the fuel supply system, such as an alternator to charge the battery or capacitor.